The use of air pressure or vacuum to induce separation of kernels of grain from a bulk quantity has been suggested in U.S. Pat. Nos. 792,958; 1,006,984; 1,046,199; 1,331,235; 1,762,671; 2,031,713; 2,384,820; 2,479,534; 2,525,718; 2,605,017; 2,737,314; 2,960,258; 2,986,305; 2,991,909; 2,995,274; 3,100,462; 3,133,676; 3,142,274; 3,156,201; 3,240,175; 3,322,080; 3,380,626; 3,387,746; 3,412,908; 3,434,437; 3,542,242; 3,608,787; 3,637,108; 3,680,373; 3,698,332; 3,721,842; 3,762,603 and 3,788,518 and British patent 802,899.